Written by Michael Vu
The screech of your alarm signals the beginning of a new day. You open your eyes to hit snooze, but to your disbelief, everything is pitch black. You realize you can’t check Instagram on your phone, nor can you tell what time it is. You start thinking about whether you could be blind. How common is total visual impairment? Surprisingly, in American adults alone, nearly 7.5 million people were reported to have significant vision loss as of 2014 [1]. But what does it mean to be totally blind? To understand the science behind blindness, we need to look at the basics of our visual system.
Our eyes don’t directly pick up pictures, they pick up electromagnetic light rays. For there to be sight, a light source — artificial or natural — must be shining on the area of focus. From there, light waves bounce off the object at different wavelengths. Our eyes, if in they’re right orientation, pick up these light waves. In the backs of our eyes, there are a group of cells called photoreceptor cells that can be categorized into two types: rods and cones. Rods are responsible for picking up light, while cones are responsible for the color aspect of our vision. Once light waves hit these cells in the back of our eyeball, they are then constructed into an image and sent to the part of the brain responsible for processing visual stimuli, called the visual cortex [4]. With this in mind, what exactly goes wrong when one goes blind?
When someone is considered to be totally blind, it means that there is no communication between the eyes and the visual cortex. This is usually because either the photoreceptor cells or the optical nerve has been damaged in some way. The reason for this damage could be a result of very many factors. For some, vision loss can be genetically caused, where photoreceptor cells die off when the patient is young. More commonly however, vision loss comes from aging, because aging increases the chances of developing glaucoma, which if left untreated, increases the pressure of your eyeball and leads to permanent optical nerve damage [3].
Fortunately, in 2013, the Argus II was approved in the U.S. as a prosthetic option for people with severe or complete vision loss. The implantation process, however, is not simple. Doctors must first surgically remove enough of the fluid inside the eye to appropriately fit the prosthetic in the eye. The light sensing implant is then secured onto the retina while cables are neatly led to the surgically attached processor located where the photoreceptor cells originally stood. Once this setup is complete, the retinal implant acts as a camera while the processor and its sixty electrodes send electrical signals, bypassing damaged areas to our visual cortex for processing [2,5]. Ultimately, this device can partially restore vision!
However, as amazing as this device sounds, it comes with a price. At nearly $150,000, the commercialization of this device is still being worked on [2]. It is expected though, that it’ll be more readily available for mass production in the next couple of years.
References:
1. “Blindness Statistics | National Federation Of The Blind”. Nfb.org. N. p., 2017. Web. 31 Jan. 2017.
2. “Second Sight Argus® II Retinal Prosthesis System”. Secondsight.com. N. p., 2017. Web. 31 Jan. 2017.
3. “Optic Nerve Damage”. Healthgrades.com. N. p., 2014. Web. 31 Jan. 2017.
4. “Visual System”. Skidmore.edu. N. p., 2017. Web. 31 Jan. 2017.
5.da Cruz,Lyndon et al.”The Argus II Epiretinal Prosthesis System Allows Letter And Word Reading And Long-Term Function In Patients With Profound Vision Loss”. British Journal of Ophthalmology 97.5 (2013): 632-636. Web. 31 Jan. 2017.